Insects have excellent ability to adapt to environment and have the widest species on earth (Wilson, O. and F. N. Peter., Biodiversity., 1989, Washington, D.C. Natl. Acad. Press). Some of those insects harm to various major crops. Chemical insecticides have been used to control such pests. But such chemical insecticides have killed not only pests but also useful insects and parasites living in pests because of their wide spectrum. In addition, target pests cannot be controlled anymore by having resistance against chemical insecticides owing to the repeated exposure on them. Further, chemical insecticides are harmful for human body.
Various plants, trees and grasses are growing widely in golf courses, so that the appearance of pests is unique and the number of pests adapting to such ecosystem is increasing year after year. As a kind of soil pests, Mimela splendems (gold bug) is a euryphagous pest harming plants (42 families, 186 species), especially plants of Rossaceae, Salicaceae, Fagaceae, Betulaceae and Aceraceae. Some adults of gold bugs harm leaves of crops and plants and larvae do roots of various crops and grasses, making them major target pest of golf clubs. Indirectly, adults of the gold bugs steal onto greens and away with discharges during the night, causing interruption of a course of a golf ball. (Lee et al, Korean Journal of Applied Entomology, 1997, 36, 2, 156-165; Lee, PhD Thesis, 2000). Particularly, the larvae of soil pests including gold bugs harming major crops and grasses are troublesome since they damage the roots of plants and grasses. The larvae of gold bugs developing and living in golf courses directly harm grass roots to death and indirectly provide themselves as feed for birds, causing digging up the grass. Therefore, they have a bad effect on the preservation of grass quality.
To control such soil insects like gold bugs, fenitrothion emulsion, chlorpyrifos-methyl emulsion and ethoprophos granules have been used. But those chemical pesticides have effects on only just-hatched larvae (the first larva stage). Thus, catching the right time is essential for controlling those insects. By the way, those chemical pesticides weaken the grass and cause overdose (Korea Patent Application #1999-15472).
Great efforts have been made to control the soil pests like gold bugs, Encarcia formosa, Eretmocerus eremicus, Plutella xylostella, Spodoptera litura and Nilaparvata lugens. But using the conventional chemical pesticides causes not only high expense but also such problems that the destruction of ecosystem, the under water contamination, the residual toxicity in agricultural products and the appearance of insects having resistance. Thus, it is urgently required to develop an environment-friendly controlling method for controlling soil pests in order to minimize such problems.
As one way of environment-friendly controlling methods for pests, insect pathogenic microorganisms are now being used, which is characterized by working selectively for target pests only without harming human, animals and plants.
For the development of a microorganism for controlling soil pests, it is very important to determine the components and factors of medium for mass-production. Again, it is essential to prepare inexpensive and available medium in order to supply microbial insecticides that are less expensive than conventional chemical insecticides. Though, it is still hard to prepare such medium for mass-production since the growth speed and time of a target microorganism as well as biological, chemical and physical factors for the production ought to be considered together.
Thus, the present inventors have searched insect pathogenic microorganisms for controlling soil pests harming major crops and finally accomplished this invention by confirming the fact that a fungus of Paecilomyces genus killed soil pests including the larvae of gold bugs.